The discovery has added to rumours that the iPad 3 will launch in March and feature a fractionally thicker design and a significantly higher resolution display.

In a list of devices in the new iOS 5.1 software, ‘iPad3,3’ is referenced, with further references to the software calling for its ‘vendorID’, ‘deviceID’ and other details.

Elsewhere in the new code, blog 9to5mac claims a reference to iPad 2,4 could be about a version of the current iPad 2 with either a version of next-generation network LTE or WiMax technology.

Apple is reported to be working on two different prototypes for the iPad 3, and is also examining the possibility of a smaller 7.85” version as well.

Analyst Richard Shim told CNET that Samsung, Sharp and LGD are all working on a high resolution screen in the style of the 4S’s ‘retina display. He claimed it would be QXGA, with a resolution of 2048x1536.

Shim said that the three suppliers were necessary to ensure sufficient manufacturing volume. CNET wrote that “the 2048x1536 screen will be the centerpiece the of next-generation iPad, or so-called iPad 3. That resolution is a quantum leap over iPad 2 which uses a more pedestrian 1024-by-768 display”.

Manufacturing was set to ramp up in time for a March launch, it has been claimed, and Apple is likely to examine a smaller model if Amazon’s rival Kindle Fire tablet stokes interest in the 7” form factor.

The iOS 5.1 code also refers to an updated version of the Apple TV, codenamed 3,1.